An increasing number of applications are requiring systems that employ a single antenna designed to receive RF energy from multiple satellites positioned in several orbital slots broadcasting at multiple frequencies. In cases where the satellites are very close to each other, it creates a challenge for reflector antenna systems often resulting in compromised performance and/or increased cost and complexity. On a given reflector system a feed (horn or radiating element) is needed to receive signals from each satellite.
A typical mobile satellite antenna has a stationary base and a satellite-following rotatable assembly mounted on the base for two- or three-axis rotation with respect to the base. The assembly includes a primary reflector, a secondary shaped sub-reflector, and a low-noise block down-converter. It may also include gyroscopes for providing sensor inputs to the rotatable assembly's orientation-control system. A typical configuration of this satellite antenna mounting approach is disclosed in U.S. Pat. No. 7,443,355.
U.S. Pat. No. 5,835,057 discloses a mobile satellite communication system including a dual-frequency antenna assembly. This system is configured to allow for the Ku band signals containing video and image data to be received by the antenna device and the L band signals containing voice/facsimile to be both received and transmitted by the antenna device on a moving vehicle.
U.S. Pat. No. 7,224,320 discloses an antenna device capable of reception from (and/or transmission to) at least three satellites of three separate RF signals utilizing a basic offset reflector on a stationary platform. This device allows for digital broadcast signals from digital video broadcast satellites in Ka, Ku and Ka frequency bands on the stationary platform.
U.S. Pat. No. 5,373,302 discloses an antenna device capable of transmission of three or more separate RF signals using a primary reflector and a frequency selective surface sub-reflector on a stationary platform. However, the patent fails to disclose the antenna device on a moving platform and also fails to disclose any time of movement of the reflector including its components to track separate frequency signals.
U.S. Pat. No. 6,593,893 discloses a multiple-beam antenna system employing dielectric filled feeds for multiple and closely spaced satellites. However, in this system, the two satellites disclosed are stationary above the earth's equatorial plane and are restricted to be spaced two degrees of arc apart in their geostationary positions. Further, the patent also fails to disclose providing the antenna system on a moving platform with a skew mechanism to simultaneously align the multiple beams with the corresponding multiple satellites across the geostationary orbital arc.
Thus there is a need to provide an improved antenna system that allows for simultaneous reception of at least two different satellite signals, e.g., high definition television (HDTV) signals in Ku and Ka frequency bands on a moving platform.